JPH02105874A - Production of copper powder for conductive coating material - Google Patents

Abstract

PURPOSE:To obtain a copper powder for conductive coating material improved in the storage stability and environmental resistance of both the copper powder itself and the conductive coating material by surface-coating a copper powder with a metal salt of a fatty acid and further treating it with an organozirconate compound. CONSTITUTION:The purpose powder is obtained by surface-treating a copper powder with a metal salt of a fatty acid and further treating it with an organozirconate compound. Examples of the preferred fatty acid include stearic, palmitic, oleic and capric acids. Examples of the metal include lead, barium, zinc, cadmium, and sodium. Examples of the treated copper powder include one treated with an amine. Examples of the amine used in this treatment include hydroxylamines of the formula (wherein R<1> is a hydroxyalkyl having at least one hydroxyl group; R<2> is an alkyl or H; and 1<=n<=3).

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for producing copper powder for conductive paint, and more specifically, to a method for producing copper powder for use in conductive paint without reducing the conductivity and electromagnetic shielding effect of copper powder. , relates to a method for producing copper powder for conductive paints that improves the storage stability and environmental resistance of the copper powder itself and the conductive paint.

[Conventional technology]

As one type of electromagnetic wave shielding material that protects electronic devices from electromagnetic interference, there are conventional conductive paints in which conductive fillers such as nickel powder, silver powder, copper powder, and carbon powder are mixed with various binder resins. This paint is applied to the surface of the plastic molded product using a spray brush or the like, and this coating shields electromagnetic waves. Among various conductive paints, copper-based conductive paints are cheaper than conductive paints using silver powder or nickel powder, and have excellent shielding effects.

However, copper powder itself and copper-based conductive paints have poor stability because the copper powder aggregates in the paint, making it difficult to obtain a good dispersion state, and moreover, they are easily oxidized in environments such as heat and humidity. However, there is a problem in that environmental resistance and conductivity are likely to deteriorate (attenuation of shielding effect). Various proposals have been made in the past to solve this problem. For example, a conductive coating composition (Japanese Unexamined Patent Application Publication No. 60/1983) is prepared by using electrolytic copper powder with an organic carboxylic acid together with a binder resin and an organic solvent.
-28273), surface treatment of copper powder with a coupling agent (Japanese Patent Laid-Open No. 60-30200), and coating copper powder with organic titanate (Japanese Patent Laid-Open No. 59-1746).
61) and a method for producing coated copper powder in which copper powder is coated with organic aluminum (Japanese Patent Application Laid-open No. 179671/1983).

[Problem to be solved by the invention]

However, although conventional coated copper powder exhibits a certain degree of environmental resistance, it does not have environmental resistance that reaches a practical level. In particular, the resistance value during heat aging increased significantly.

This invention has been made based on the above-mentioned background, and its purpose is to eliminate the drawbacks of the conventional copper powder for conductive paints and conductive paint compositions, and to improve the conductivity of copper powder and electromagnetic shielding. It is an object of the present invention to provide a method for producing copper powder for conductive paint that significantly improves the environmental resistance of the copper powder itself and the paint composition without reducing the effectiveness. [Means for solving the problem] The above problem is achieved by: This is achieved by the method for producing copper powder for conductive paint according to the present invention. That is, the manufacturing method of this invention is
This method is characterized in that the surface of the copper powder is treated with a fatty acid metal salt, and then further treated with an organic zirconate compound.

In a preferred embodiment of this invention, the fatty acid metal salt may be a stearate metal salt, a palmitate metal salt, an oleate metal salt, or/and a capric acid metal salt.

In another preferred embodiment of the present invention, lead fatty acid, barium fatty acid, zinc fatty acid, cadmium fatty acid and/or sodium fatty acid can be used as the fatty acid metal salt.

In yet another embodiment, amine-treated copper powder can be used as the copper powder to be treated, that is, as the copper powder to be treated with a fatty acid metal salt.

This invention will be explained in more detail below.

Copper powder The shape of the copper powder used in this invention can be obtained by electrolytic method, reduction method,
There are dendritic, granular, acicular, and spherical shapes obtained by the atomization method, and there are also flake shapes obtained by mechanically processing these with a ball mill or the like.

Further, dendritic copper powder, flaky copper powder, granular copper powder, and spherical copper powder can be mixed and used using a V-type mixer or the like.

Pretreatment of Copper Powder The raw material copper powder that can be used in this invention includes metals such as silver, nickel, zinc 1, and palladium, alloys such as solder, and organic compounds such as amines, amino acids, carboxylic acids, and their derivatives. It may be coated in advance.

In a preferred embodiment of this invention, the untreated copper powder can be treated with an amine. The amine to be treated is
For example, there is hydroxylamine represented by the following structural formula.

(R) NCR2) n 3-n (wherein, R1 represents a hydroxyalkyl group having at least one hydroxyl group, R2 represents an alkyl group or hydrogen, and n satisfies the condition of 1≦n≦3) (representing an integer that satisfies) such hydroxyalkylamines, for example,
Examples include monoethanolamine, N,N-dimethylethanolamine, N,N-diethylethanolamine, jetanolamine, N-butylgetanolamine, triethanolamine, triisopropanolamine, and monoisopropanolamine. This treatment method with hydroxyalkylamine includes a wet method such as a method in which copper powder is placed in an aqueous amine solution, stirred and immersed, and then filtered, and a method in which the aqueous amine solution is directly sprayed onto the copper powder. When processing by this wet method, it is desirable to subject the material to a drying step in order to substantially remove residual moisture after processing. There is also a dry method in which amine is directly added to copper powder and mixed using a mixer or mill.

The copper powder to be treated may also be pre-treated, if necessary.
The oxidized coating from the surface of the copper powder is removed using reagents such as inorganic acids, organic acids, various reducing agents, and by hydrogen reduction.

Further, the copper powder to be treated may be dried as a pretreatment.

Fatty acid metal salt In the method of this invention, copper powder is first treated with a fatty acid metal salt.

Examples of fatty acid metal salts include stearic acid, valmitic acid,
Higher fatty acids such as oleic acid, lead, barium, zinc,
There are metal salts such as cadmium and sodium. Particularly preferred is lead stearate.

The amount of fatty acid metal salt to be treated is 0.5 ppm to 20% by weight, preferably 1 ppm to 20% by weight, based on the weight of copper powder, in terms of metal content.
It is 10% by weight. This is because the environmental resistance of copper powder starts to gradually decrease below lppm, and this tendency becomes remarkable when it becomes less than 0.5 ppm. Also, when it exceeds 10% by weight, the conductivity of copper powder gradually decreases. Starts to decrease, 20% by weight
This is because the tendency becomes more pronounced when the value is exceeded.

The treatment of copper powder with a fatty acid metal salt is preferably carried out in a non-liquid state. That is, a powdered fatty acid metal salt is dry mixed with copper powder using a mixer such as a mixer or a kneader.

By this mixing, the fine powder of fatty acid metal salt is completely and uniformly scattered and adhered to the surface of the copper powder.

Organic Zirconate Compound In the method for producing copper powder for conductive paint according to the present invention, copper powder treated with a fatty acid metal salt is coated with an organic zirconate compound. Preferred zirconium compounds have at least 1
It has at least one easily hydrolyzable organic group and at least one hydrolyzable lipophilic group.

Such compounds include, for example, isopropyltriisostearoylzirconate, isopropyltridodecylbenzenesulfonylzirconate, isopropyltris(dioctylpyrophosphate)zirconate, tetraisopropylbis(dioctylphosphate)zirconate, tetraoctylbis(ditridecylphosphite). Zirconate, tetra(2,2-diallyloxymethyl-1-butyl)bis(di-tridecyl)phosphite zirconate, bis(dioctylpyrophosphate)oxyacetate zirconate, bis(dioctylpyrophosphate)ethylenezirconate, isopropyl trio Cutanoyl zirconate, Isopropyl dimethacryliisostearoyl zirconate, Isopropyl isostearoyl diacryl zirconate, Isopropyl tri(dioctyl phosphate) zirconate, Isopropyl tricumylphenyl zirconate, Isopropyl tri(N-aminoethyl-aminoethyl) zirconate, Dioctanoyl zirconate Examples include mylphenyloxyacetate zirconate and diisostearoyl ethylene zirconate.

Zirconate compounds preferred in terms of performance are obtained by the reaction of zirconium alkoxides with carboxylic acids, especially higher fatty acids. For example, several times the mole of tetraalkoxyzirconium, for example, 2 to 5 moles of higher saturated fatty acids such as isostearic acid, palmitic acid, mystirilic acid, lauric acid, capric acid, their isomers, oleic acid, linoleic acid, etc. React acids, higher unsaturated fatty acids such as linuric acid, and their isomers.

The amount of the organic zirconate compound to be treated is 0.005 to 20% by weight, preferably 0.01 to 10% by weight, based on the weight of the copper powder. This means that if it is less than 0.01% by weight, the dispersibility of copper powder in the conductive paint will gradually decrease;
If it is less than 5% by weight, the oxidation resistance will further deteriorate and the dispersibility will tend to decrease significantly, and if it exceeds 10ffij 1%, the conductivity of the copper powder will gradually decrease, and if it exceeds 20% by weight, this tendency will decrease. This is because it becomes significant.

A coating treatment method using an organic zirconate compound includes a method of adding a necessary amount of the organic zirconate compound to copper powder, dry mixing and stirring with a mixer such as a mill or mixer, and coating the copper powder.

Conductive Coating Composition The conductive coating composition using copper powder of the present invention contains copper powder coated with a fatty acid metal salt and an organic zirconate compound, a resin binder, and a solvent.

Binders that can be used in this invention include:
Usually, it has good adhesion to plastics often used in electronic devices.

For example, acrylic resin, polyurethane resin, polyester resin, styrene resin, phenol resin, epoxy resin, etc. can be used for electronic device plastics such as ABS, polystyrene, and polycarbonate.

In addition, solvents that can be used in this invention include toluene, thinner, hexane, benzene, methyl ethyl ketone, xylene, methyl alcohol, ethyl alcohol, propyl alcohol, butyl alcohol, methyl isobutyl ketone, which can dissolve additives such as binders, One or a mixture of two or more organic solvents such as ethyl acetate, butyl acetate, methyl cellosolve, and ethyl cellosolve are preferred.

The copper powder blended into this composition is 40 to 9% by weight based on the solid content of the conductive composition, and preferably,
It is 50-85% by weight.

The amount of the binder added to this composition is 10 to 60% by weight, preferably 15 to 50% by weight, based on the solid content of the conductive composition.

In addition to the above components, various additives can be included depending on the purpose. Such agents include reducing agents, surfactants, antioxidants, antifoaming agents, thickeners, thixotropic agents, rust preventives, and flame retardants.

[For production]

In the present invention having the above-described structure, fine powder of fatty acid metal salt adheres to the surface of the copper powder particles in a scattered manner to form a rust-preventing film on the copper powder. The organic zirconate compound treated with the fatty acid metal salt has a hydrophilic organic group that is easily hydrolyzed and a lipophilic organic group that is difficult to be hydrolyzed, with a zirconium atom as the center, and a hydrophilic organic group that is difficult to be hydrolyzed. Since the hydrophilic group (for example, an alkoxy group) causes a displacement reaction with the water adsorbed on the surface of the copper powder, molecules of the organic zirconate compound are formed on the surface of the copper powder with the hydrophilic part on the inside and the hydrophobic part on the outside. They are arranged to form a rust preventive film. Therefore, a molecular film is formed firmly and well on the surface of the copper powder, and high hydrophobicity is imparted to the surface of the copper powder. This hydrophobic film acts to protect the copper powder from the external environment such as heat and humidity without impairing conductivity, and serves as a rust-preventive film. Also,
This film is composed of resin binder molecules and van der Waals forces, hydrogen bonds, ionic bonds,
The copper powder is skillfully intertwined by covalent bonds, and the shear stress generated during the stirring and kneading process forms a good dispersion state of the copper powder.

〔Effect of the invention〕

As demonstrated from the examples below, claims 1.2 and 3
With the manufacturing method of coated copper powder for conductive paint, the surface of copper powder particles is coated with fatty acid metal salt and organic zirconate compound, so it is possible to improve heat resistance, moisture resistance, and environmental resistance without impairing conductivity. can.

The conductive paint composition using the coated copper powder for conductive paint obtained by the manufacturing method of claims 1.2 and 3 has excellent storage stability by dispersing the copper powder well, and the coating film thereof is can be imparted with environmental resistance such as excellent heat resistance.

In the method for producing copper powder for conductive paint according to claim 4, since the copper powder is pretreated with amine, the antirust effect of the copper powder can be further enhanced.

〔Example〕

The present invention will be specifically explained below based on Examples and Comparative Examples, but the present invention is not limited to the following examples unless it exceeds the gist thereof.

Experimental example A (aspect without amine pretreatment) experimental materials The materials used in Examples and Comparative Examples are shown below.

The dendritic electrolytic copper powder (MF-D2, manufactured by Nil Metal Mining Co., Ltd.) used in this example is shown in Table A1.

Table 81 Characteristic apparent density of copper powder 0.72 g/d tap density
1.30g/cd specific surface area
0.34rrr/g average particle size 11.8
μm The fatty acid metal salts used in this example and comparative samples are shown in Table 82 below.

No.

2-I No.

Table 82 Fatty acid metal salts Lead stearate Barium stearate Zinc stearate Caddonium stearate Sodium stearate Comparison sample Isopropyl tridodecylbenzenesulfonyl titanate Tetraisobupylbis(dioctylphosphite) titanate A2-8 Acetalkoxyaluminum diisopropylate A2-9 Anthrazine A2-10 7-methacryloxypropyltrimethoxysilane The organic zirconate compound used in this example is
It was prepared from the metal alkoxide and higher fatty acid shown in the table.

Table 83 Organic zirconate compound No. Number of moles of metal alkoxide Number of moles of higher fatty acid A3-1 Tetra-n-butoxy 1 Syzylconium isostearate 1 1 1 1 1 1 Oleic acid Balmitic acid Isostearic acid Lauric acid Capric acid mistyric acid Experimental example A1 Heat resistance and moisture resistance of copper powder The fatty acid metal salts and comparative sample shown in Table 82 were added to the dendritic copper powder shown in Table 81 above, each having a metal content of 1.100.
500 ppm and 0.1.1.0.5.0.10.0% by weight were added in a dry state and uniformly mixed using a mixer for treatment. A portion of the treated copper powder was treated with an organic zirconate compound shown in Table 83. The copper powder with the surface coating formed thereon was left for 2000 hours in an environment of a temperature of 85° C. and a humidity of 60° C./95% RH, and the appearance of discoloration and patina of the copper powder was observed. The processing amount of each organic zirconate compound is 0.05.0, 1.0. 5.
An experiment was conducted by changing the amount to 1.0.5.0.10% by weight.

As a result, fatty acid metal salts shown in Table 82 and organic zirconate compounds shown in Table 83 (No.

When treated with A3-1 to A3-7), there was no discoloration at all and no patina occurred at a fatty acid metal salt treatment amount of ippm to 10% by weight. In contrast, Table 82 (No, A2
Copper powder treated only with the fatty acid metal salts of -1 to 10) and the comparative sample had significant brownish discoloration and development of patina.

From the above results, it can be seen that the coated copper powder of the present invention has excellent heat resistance, humidity resistance, and aging resistance at high temperatures and high humidity.

Experimental Example A2 Conductive coating of coating film A conductive paint was prepared from the surface-coated copper powder used in Experimental Example A1 using an acrylic resin (solid content: 60% by weight) and toluene as a solvent.

The obtained conductive paint was printed on an acrylic plate vertically by 2css horizontally by a screen printer. A conductor circuit with a film thickness of 40±10 μm was formed. The volume resistivity of this circuit was measured.

As a result, fatty acid metal salts shown in Table 82 and organic zirconate compounds (No.

The circuit obtained from the conductive paint containing coated copper powder according to this invention treated with A3-1 to 7) is 3.0X10' to 4
．． It had a volume resistivity of 0XIO-'Ω'0111.

On the other hand, the circuit obtained from the conductive paint containing copper powder treated only with the fatty acid metal salt and the comparison sample was 1.0X
It exhibited a volume resistivity of 10-3 to 2.0 x 10-3 Ω.

This result shows that the conductive paint containing the coated copper powder according to the present invention exhibits good conductivity.

Experimental Example A3 Heat and Moisture Resistance of Coating Film The conductor circuit board prepared in Experimental Example A2 was heated to a temperature of 85°C.
The coating film was left to stand for 2000 hours in a humidity environment of 60° C./95% RH, and the rate of change in resistance of the coating film was measured.

As a result, in a high temperature environment of 85°C, the coated copper powder according to the present invention treated with the fatty acid metal salt shown in Table 82 and the organic zirconate compound (No. A3-1 to A3-7) shown in Table 83 The coating film obtained from conductive paint was at least 5% and at most 10%. On the other hand, coatings obtained from conductive paints containing copper powder treated with comparative samples showed significant changes, from as low as 55% to as much as 150% to 190%.

In a humidity environment of 60° C./95% RH, the coated copper powder according to the present invention treated with the fatty acid metal salt shown in Table 82 and the organic zirconate compound (No. A3-1 to A3-7) shown in Table 83 was The coating film obtained from the conductive paint containing such a material was at least 15% and at most 3%. On the other hand, coatings obtained from conductive paints containing copper powder treated with comparative samples showed significant changes of as little as 44% and as much as 115% to 135%.

Experimental example B (aspect of amine pretreatment) experimental materials The materials used in Examples and Comparative Examples are shown below.

The dendritic electrolytic copper powder (MF-B2, manufactured by Nil Metal Mining Co., Ltd.) used in this example is shown in Table 'MB1.

Table 81 Characteristics of copper powder Apparent density 0.72g/crd Tap density 1.30g/c#i Specific surface area
0.34ba/g average particle size 11,
8 μm The fatty acid metal salts used in this example and comparative samples are shown in Table 82 below.

Table 82 No, Fatty acid metal salt B2-1 Lead stearate B2-2 Barium stearate B2-3 Zinc stearate B2-4 Lead valmitate B2-5 Zinc valmitate B2-6 Lead oleate B2-7 Lead caprate B2-8 Zinc caprate The organic amines used in this example are shown in Table 183 below.

Table 83 Organic amine No., Organic amine B5-1) Jetanolamine B5-2 Monoisopropanolamine B5-3
N,N-dimethylethanolamine B5-4 Jetanolamine B5-5 N-butyl jetanolamine The organic zirconate compounds used in this example were prepared from metal alkoxides and higher fatty acids shown in Table 84 below.

Table 84 Organic zirconate compound No. Metal alkoxide Higher fatty acid B4-1 Tetra-n-butoxysidylconium isostearate B4-2 Oleic acid B4-3
N Valmitic acid B4-4 Tetraisobutyric acid Syzylconium laurate B4-5 # Capric acid B4-6
N Mystyric acid B4-7 Tetra-1-butoxy syzylconium stearate Note) The molar ratio of higher fatty acid and metal alkoxide is 3:1
It is.

The comparative surface coatings used in this Example B are shown in Table 85.

Table 85 Comparative surface coating agent NOl Comparative surface coating agent B5-1 Isopropyl tridodecylbenzenesulfonyl titanate B5-2 Tetraisopropyl bis(dioctyl phosphite) titanate B5-3 Acetalkoxyaluminum diisopropylate B5-4 Anthrazine B5- 57-Methacryloxypropyltrimethoxysilane B5-6 Isocyanuric Acid Experimental Example B1 Heat and Moisture Resistance of Copper Powder The dendritic copper powder shown in Table 81 was mixed with an aqueous solution of the organic amine shown in Table 83 (each with an amine concentration of 1.0 .3.0.6.0
% by weight) for 10,30,60 minutes, separated and dried to perform amine pretreatment.

The fatty acid metal salts listed in Table 82 were added to the dried copper powder in amounts of 0, 5, 1, 5, 10, 100, and 500 ppm, respectively, in terms of metal content.
, 0.01.0, 5.1.0% by weight added in dry state,
The mixture was mixed and treated in a ceramic pot for 1.2.3 hours.

The treated copper powder was treated with the organic zirconate compounds shown in Table 84 in the same manner as described above. The copper powder with the surface coating formed was heated at a temperature of 85°C and a humidity of 60°C/95% RH for 20 minutes.
The copper powder was left to stand for 00 hours, and the appearance of discoloration and patina of the copper powder was observed. The processing amount of each organic zirconate compound is 0.05.0.1.0.5.1,0.0.
An experiment was conducted by changing the amount to 3.0% by weight. As a result of the observation, the surface-coated copper powder according to the present invention did not change color at all.

Further, the dendritic copper powder shown in Table 81 is treated with the fatty acid metal salt shown in Table 82 in water, ethanol, or toluene solvent, and then the copper powder is treated in the same manner with the organic zirconate compound shown in Table 84. Then, the copper powder with the surface coating formed was heated to 85
The copper powder was left for 2,000 hours in a humidity environment of 60° C./95% RH, and the appearance of discoloration and patina of the copper powder was observed. As a result, there was significant brownish discoloration and partial patina development.

Furthermore, copper powder was treated with the comparative surface coating agent shown in Table 85 in the same manner as described above, and the copper powder with the surface coating formed was heated at 85°C.
The copper powder was left for 2000 hours in a humidity environment of 60° C./95% RH, and the appearance of discoloration and patina of the copper powder was observed. As a result, there was brownish discoloration and patina (young).

From the above results, it can be seen that the coated copper powder of the present invention has excellent heat resistance, humidity resistance, and aging resistance at high temperatures and high humidity.

Experimental Example B2 Conductivity of Coating Film A conductive paint was prepared from the surface-coated copper powder used in Experimental Example B1 using an acrylic resin (solid content: 60% by weight) and toluene as a solvent.

A conductor circuit was formed from the obtained conductive paint, and the volume resistivity of this circuit was measured.

As a result, fatty acid metal salts shown in Table 82 and organic zirconate compounds (NO2B4-1 to 7
) The circuit obtained from the conductive paint containing the coated copper powder according to the invention treated with
It had the highest volume resistivity of the country.

On the other hand, circuits obtained from conductive paints containing copper powders treated in water, ethanol, toluene solvents and copper powders treated only with comparative surface coatings were 4×10″4 to 2×1
It showed a volume resistivity of 0'Ω·.

This result shows that the conductive paint containing the coated copper powder according to the present invention exhibits good conductivity.

Experimental Example B3 Heat and Moisture Resistance of Coating Film The conductor circuit board prepared in Experimental Example B2 was heated to a temperature of 85°C.
The coating film was left to stand for 2000 hours in a humidity environment of 60° C./95% RH, and the rate of change in resistance of the coating film was measured.

As a result, in a high temperature environment of 85°C and a humidity environment of 60°C/95% RH, the fatty acid metal salts shown in Table 82 and the organic zirconate compounds shown in Table 84 (No. B4-1 to B4-7)
At most, only 5% of the coating was obtained from conductive paints containing coated copper powder according to the invention treated with . On the other hand, coatings obtained from conductive paints containing copper powders treated in water, ethanol, toluene solvents and copper powders treated only with comparative surface coatings showed at least 10-20% and at most 150% % to 170%.

From these results, the coating film obtained from the copper powder according to the present invention has excellent heat resistance and moisture aging resistance.

Claims (1)

[Scope of Claims] 1. A method for producing copper powder for conductive paint, which comprises treating the surface of copper powder with a fatty acid metal salt and then further treating with an organic zirconate compound. 2. The method for producing copper powder for conductive paint according to claim 1, wherein the fatty acid metal salt is a stearic acid metal salt, a palmitic acid metal salt, an oleic acid metal salt, or/and a capric acid metal salt. 3. The method for producing copper powder for conductive paint according to claim 1, wherein the fatty acid metal salt is fatty acid lead, fatty acid barium, fatty acid zinc, fatty acid cadmium, and/or fatty acid sodium. 4. The method for producing copper powder for conductive paint according to claim 1, wherein the copper powder treated with the fatty acid metal salt is amine-treated.